1. Field of the Invention
The present invention relates to a multi-feed detection apparatus which is mounted in an image processing apparatus such as a copying machine, scanner, facsimile machine, or printer, and detects whether multi-feed of a plurality of sheets has occurred, a sheet conveyance apparatus including the multi-feed detection apparatus, and a sheet processing apparatus such as an image reading apparatus or image forming apparatus.
2. Description of the Related Art
A scanner, printer, copying machine, printing machine, ATM (Automated Teller Machine), and the like have a mechanism of separating and conveying sheet-like members one by one. However, multi-feed may occur, in which when only one sheet-like member should be conveyed, two or more sheet-like members are conveyed while overlapping each other partially or entirely. To prevent this, an apparatus which conveys a sheet-like member requires a function of detecting multi-feed of sheet-like members. As the mechanism of detecting multi-feed of sheet-like members, a multi-feed detection apparatus using an ultrasonic wave has prevailed.
In the multi-feed detection apparatus, it is known that when a sheet-like member is irradiated with an ultrasonic wave, the ultrasonic wave is partially reflected by the sheet surface and the reflected wave is diffusely reflected between the sheet surface and an ultrasonic transmitter. An ultrasonic receiver sometimes receives the diffusely reflected wave as a noise component, and the noise component generated by diffuse reflection degrades the sensor performance. To solve this, an arrangement of emitting an ultrasonic wave obliquely to the sheet surface is employed (see Japanese Patent Laid-Open No. 2007-276965).